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Could simple anger have taught people to cooperate?

June 20, 2011
Special to World Science  

While re­search­ers don’t agree on how hu­mans first de­vel­oped the ex­cep­tion­al lev­el of coop­era­t­ion they show in to­day’s so­ci­eties, a few bas­ic ideas are of­ten ban­died about the sci­en­tif­ic lit­er­a­ture.

A new study is chal­leng­ing one of the lead­ing the­o­ries, though, to re­place it with a sim­pler no­tion: hu­mans learn­ed to coop­erate be­cause they did­n’t want to make the neigh­bors an­gry.

The re­search forms a coun­ter­point to a grow­ing stack of stud­ies ar­gu­ing that police-like be­hav­iors play lead­ing roles in the de­vel­op­ment of coop­era­t­ion, by help­ing to en­force stan­dards of con­duct.

How coop­era­t­ion became com­mon in any so­cial spe­cies has long been a ma­jor ques­tion mark. Ev­o­lu­tion­ary the­o­ry, the main tool biologists use to ex­plain such things, fails to di­rectly ex­plain this one, and on the sur­face in fact seems to in­di­cate it could not happen.  Yet all sorts of crea­tures coop­erate—and hu­mans, sci­en­tists say, are the only ones who coop­erate in large groups with non-kin and strangers.

Pro­pos­ing that some mem­bers of a com­mun­ity tend to take on polic­ing roles, self-ap­pointed or oth­er­wise, is a po­ten­tial so­lu­tion that has in­trigued many re­search­ers. It has a tan­ta­liz­ing ba­sis in bi­ol­o­gy: crea­tures as sim­ple as bac­te­ria have been doc­u­mented to adopt police-like be­hav­iors to up­root freeload­ers and cheaters from their midst. Re­search­ers such as Ernst Fehr of the Uni­vers­ity of Zu­rich have en­listed peo­ple in game-ex­pe­ri­ments in which they can win mon­ey if they’re gen­er­ous among each oth­er—but may win more by free­load­ing on the larg­er group’s gen­eros­ity, at some cost to the group. When play­ers al­so have a chance to fi­nan­cially pe­nal­ize these free-riders, they do so even if it hurts them—and coop­era­t­ion goes up, Fehr and col­leagues found. Math­e­mat­i­cal mod­els have al­so been drawn up show­ing how such “third-par­ty pun­ish­ment,” or pun­ish­ment on be­half of a com­mun­ity, can make sense as part of an ev­o­lu­tion­ary pic­ture.

But re­search­ers in­clud­ing Frank J. Mar­lowe of the Uni­vers­ity of Dur­ham, U.K., ar­gue that the­re’s one prob­lem he­re. In the sim­plest real hu­man so­ci­eties, peo­ple who pun­ish oth­ers on be­half on the pub­lic good seem to be woe­fully few, yet shar­ing and coop­era­t­ion are still com­mon. In a new stu­dy, Mar­lowe, with a group of U.K. and U.S. col­leagues, claim that the avengers of the wronged are un­nec­es­sary to ex­plain hu­man coop­era­t­ion—ex­cept if we’re talk­ing about peo­ple aveng­ing them­selves.

“Mo­ti­vated by the bas­ic emo­tion of anger,” peo­ple’s ten­den­cy to re­tal­i­ate on their own be­half is “suf­fi­cient to ex­plain the ori­gins of hu­man coop­era­t­ion,” the re­search­ers wrote in the July 22 is­sue of the re­search jour­nal Pro­ceed­ings of the Roy­al So­ci­e­ty B. 

This ten­den­cy is “more un­iver­sal” than pun­ish­ment of wrong­do­ers on be­half of third par­ties, they added, la­bel­ing this di­rect sort of re­talia­t­ion “sec­ond par­ty, ‘spite­ful’ pun­ish­ment.”

Mar­lowe and col­leagues drew on pub­lished de­scrip­tions of small-scale for­ag­ing so­ci­eties that plau­sibly could have been like early hu­man com­mun­i­ties. They al­so drew on the re­sults of ad­di­tion­al ex­pe­ri­men­tal games, these con­ducted with mem­bers of such small so­ci­eties as well as larg­er ones. The games were aimed at gaug­ing peo­ple’s will­ing­ness to be gen­er­ous and, on the flip side, to re­tal­i­ate for un­co­op­er­a­tive be­hav­ior.

These ex­pe­ri­ments and de­scrip­tions, they said, show that small so­ci­eties are less gen­er­ous and less giv­en to en­gage in “third-par­ty pun­ish­ment” than large so­ci­eties. How­ev­er, their mem­bers are eve­ry bit as will­ing to avenge them­selves, even at a cost, they added.

Third-par­ty, police-like pun­ish­ment, termed “strong re­cipro­city,” is “more rel­e­vant for un­der­stand­ing the cul­tur­al ev­o­lu­tion of large, com­plex, agricul­tur­al so­ci­eties,” they added. The re­search group con­ducted the ex­pe­ri­men­tal games with a “wide range of so­ci­eties, in­clud­ing hunter–gathe­rers, horticul­tur­alists, pas­toral­ists, farm­ers and ­city dwellers,” they not­ed.

Sev­er­al games were played. In the sim­plest, de­signed to meas­ure gen­eros­ity, the re­searcher hands some mon­ey to a sub­ject, who is asked to give some of it to an­oth­er play­er if he or she wants. The ex­pe­ri­menter records what this first play­er de­cides to do, and the “game” ends the­re. In an­oth­er, the play­er is again asked to of­fer some of the mon­ey to an­oth­er play­er, but that oth­er play­er is ad­vised that they can re­ject the mon­ey if, for ex­am­ple, the of­fer seems in­sult­ingly small. If they re­ject the of­fer, both play­ers get noth­ing: it’s a game de­signed to gauge peo­ple’s will­ing­ness to dish out “spite­ful” pun­ish­ment.

“In real life,” such seem­ingly spite­ful be­hav­ior probably pays off eventually, Mar­lowe and col­leagues wrote, be­cause oth­ers learn they can’t easily get away with hand­ing the pun­isher a raw deal. 

In a third game, a play­er gets to pun­ish a sec­ond play­er who they feel gave a bad deal to a third play­er, by de­priv­ing them of all their al­lot­ted mon­ey. The catch is that the first play­er has to give up one-fifth of their own al­lot­ment to do this. This game is de­signed to mim­ic the role of the en­forcer who pun­ishes mis­cre­ants on be­half of so­ci­e­ty. 

The find­ings do show that in large so­ci­eties, “third-par­ty pun­ish­ment” is im­por­tant and in­deed more com­mon than di­rect re­venge, the re­search­ers found. “Pun­ish­ers may get a reputa­t­ion as good cit­i­zens and might be re­warded for en­forc­ing stan­dards of fair­ness for the larg­er group,” ex­plaining their prev­a­lence in larg­er so­ci­eties, Mar­lowe and col­leagues wrote. But peo­ple in very small so­ci­eties are “less will­ing” to do that, and in­stead more of­ten pun­ish those who have di­rectly slighted them.

“What is spe­cial about hu­mans is the will­ing­ness to be spite­ful to force coop­era­t­ion,” Mar­lowe and col­leagues con­clud­ed.


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While researchers don’t agree on how humans first developed the exceptional level of cooperation they show in today’s societies, a few basic ideas are often bandied about the scientific literature. A new study is challenging one of the leading theories, though, to replace it with a simpler notion: humans learned to cooperate because they didn’t want to make the neighbors angry. The research forms a counterpoint to a growing stack of studies arguing that police-like behaviors play leading roles in the development of cooperation, by helping to enforce standards of decent conduct. How cooperation evolved in any social creature has long been a major question mark, because evolutionary theory fails directly explain how this could happen, and on the surface seems to in fact indicate it wouldn’t. Yet all sorts of creatures cooperate—and humans, scientists say, are the only ones who cooperate in large groups with non-kin and strangers. Proposing that some members of a community tend to take on policing roles, self-appointed or otherwise, is a potential solution that has intrigued many researchers. It has a tantalizing basis in biology: creatures as simple as bacteria have been documented to adopt police-like behaviors to uproot freeloaders and cheaters from their midst. Researchers such as Ernst Fehr of the University of Zurich have enlisted people in game-experiments in which they can win money if they’re generous among each other—but may win more by freeloading on the larger group’s generosity, at some cost to the group. When players also have a chance to financially penalize these free-riders, they do so even if it hurts them—and cooperation goes up, Fehr and colleagues found. Mathematical models have also been drawn up showing that such “third-party punishment,” or punishment on behalf of a community, can make sense as part of an evolutionary picture. But researchers including Frank J. Marlowe of the University of Durham, U.K., argue that there’s one problem here. In the simplest real human societies, people who punish others on behalf on the public good seem to be woefully few, yet sharing and cooperation are still common. In a new study, Marlowe, with a group of U.K. and U.S. colleagues, claim that the avengers of the wronged are unnecessary to explain human cooperation—except if we’re talking about people avenging themselves. “Motivated by the basic emotion of anger,” people’s tendency to retaliate on their own behalf is “sufficient to explain the origins of human cooperation,” the researchers wrote in the July 22 issue of the research journal Proceedings of the Royal Society B. This tendency is “more universal” than punishment of wrongdoers on behalf of third parties, they added, labeling this direct sort of retaliation “second party, ‘spiteful’ punishment.” Marlowe and colleagues drew on published descriptions of small-scale foraging societies that plausibly could have been like early human communities. They also drew on the results of additional experimental games, these conducted with members of such small societies as well as larger ones. The games were aimed at gauging people’s willingness to be generous and, on the flip side, to retaliate for uncooperative behavior. These experiments and descriptions, they said, show that small societies are less generous and less given to engage in “third-party punishment” than large societies. However, their members are every bit as willing to avenge themselves, even at a cost, they added. Third-party, police-like punishment, termed “strong reciprocity,” is “more relevant for understanding the cultural evolution of large, complex, agricultural societies,” they added. The research group conducted the experimental games with a “wide range of societies, including hunter–gatherers, horticulturalists, pastoralists, farmers and city dwellers,” they noted. Several games were played. In the simplest, designed to measure generosity, the researcher hands some money to a subject, who is asked to give some of it to another player if he or she wants. The experimenter records what this first player decides to do, and the “game” ends there. In another, the player is again asked to offer some of the money to another player, but that other player is advised that they can reject the money if, for example, the offer seems insultingly small. If they reject the offer, both players get nothing: it’s a game designed to gauge people’s willingness to dish out “spiteful” punishment. “In real life,” such seemingly spiteful behavior probably pays off eventually, Marlowe and colleagues wrote, because others learn they can’t easily get away with handing the punisher a raw deal. In a third game, a player gets to punish a second player who they feel gave a bad deal to a third player, by depriving them of all their allotted money. The catch is that the first player has to give up one-fifth of their own allotment to do this. This game is designed to mimic the role of the enforcer who punishes miscreants on behalf of society. The findings do show that in large societies, “third-party punishment” is important and indeed more common than direct revenge, the researchers found. “Punishers may get a reputation as good citizens and might be rewarded for enforcing standards of fairness for the larger group,” explaining their prevalence in larger societies, Marlowe and colleagues wrote. But people in very small societies are “less willing” to do that, and instead more often punish those who have directly slighted them. “What is special about humans is the willingness to be spiteful to force cooperation,” Marlowe and colleagues concluded.